Mercury manometer

ABSTRACT

The high precision mercury manometer disclosed herein comprises a container exposed to atmospheric pressure and seated on one of the trays of a balance. Inserted into the container is a vertical portion of a rigid pipe which is coupled at its other end by a flexible connector, to the bottom of a second container exposed either to atmospheric pressure, or to a second pressure to be measured. The second container is displaceable vertically over the length of a scale graduated both above and below the level of the first container. The connection between the two containers constituted of the rigid and flexible conduits has a practically constant volume, irrespective of the change in location of the second container. The first container and the balance may be sealed in a closed chamber which may be exposed either to atmospheric pressure, or to a third pressure between which and the second pressure a differential pressure reading is desired. A connection is provided between the closed chamber and the second container so that the mercury level in the latter may also be subjected to the third pressure.

United States Patent Chadenson [54] MERCURY MANOMETER [72] lnventor:Pierre Chadenson, La Tronche, France [73] Assignee: Societe Generale DeConstructions Electriques Et Mecaniq'ues (Alsthom), Grenoble, France[22] Filed: Nov. 9, 1970 [21] Appl. No.: 87,855

[30] Foreign Application Priority Data Nov. 13, 1969 France ..6939387July 16, 1970 France ..7027329 [52] U.S. Cl ..73/405, 73/401 [51] Int.Cl. ..G0ll 7/18 [58] Field of Search ..73/401, 405, 296

[56] References Cited UNITED STATES PATENTS 3,515,005 6/1970 Brown..73/405 Primary Examiner-Donald O. Woodiel AttorneySylvester J. Liddy,John J. Hart, Joe E. Daniels and Charles E. Baxley [57] ABSTRACT Thehigh precision mercury manometer disclosed herein comprises a containerexposed to atmospheric pressure and seated on one of the trays of abalance. inserted into the container is a vertical portion of a rigidpipe which is coupled at its other end by a flexible connector, to thebottom of a second container exposed either to atmospheric pressure, orto a second pressure to be measured. The second container isdisplaceable vertically over the length of a scale graduated both aboveand below the level of the first container. The connection between thetwo containers constituted of the rigid and flexible conduits has apractically constant volume, irrespective of the change in location ofthe second container. The first container and the balance may be sealedin a closed chamber which may be exposed either to atmospheric pressure,or to a third pressure between which and the second pressure adifferential pressure reading is desired. A connection is providedbetween the closed chamber and the second container so that the mercurylevel in the latter may also be subjected to the third pressure.

8 Claims, 2 Drawing Figures PATENTEUJUN 6 I972 sum 1 or 2 INVENTOR.

P/ERR E Cl/ADENSON BY 2 0/ ArrakA/zy PATENTEDJun 61972 I 3,667,298

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FY5225 Cf/A DEN-SO/V A Trakw) MERCURY MANOMETER THE INVENTION Thisinvention relates to mercury filled manometers and is primarilyconcerned with the provision of an improved mercury filled monometercapable of measuring with high precision pressures differing from thatof the atmosphere and especially low pressure or partial vacuums.

In accordance with the invention, the manometer essentially includes acontainer seated on one of the trays of a balance and one verticallydisposed end of a rigid pipe extending down into a supply of liquidmercury contained therein. The rigid pipe is coupled by a conduit, atleast part of which is flexible, to the bottom of a second containerwhich also contains liquid mercury and which may be displaced verticallyalong a graduated scale extending above and below the level of themercury in the first container. This arrangement of the two containers,the rigid pipe and the connecting conduit will provide a practicallyconstant volume of mercury between the levels in the two containersirrespective of the deformation caused in the connecting conduit bychanges in level of the mercury in the second container.

The aforesaid essential construction may be utilized to measure a lowpressure or partial vacuum by first placing the second container at thesame height as the first container, exposing both containers toatmospheric pressure, and then filling the unit with mercury until bothcontainers are approximately half full and the mercury is at identicallevels in both containers. The balance is then placed in a state ofequilibrium and the height of the second container is read on thegraduated scale. To measure the low pressure or partial vacuum, themercury in the second container is exposed thereto, thereby causing thedisplacement of the mercury between the two containers and a consequenttilting of the balance. The second container is then displaced along thelength of the graduated scale until the equilibrium of the balance isrestored at which time the level of the mercury in the first containerwill have been restored to its original height. The new height of thesecond container is then read on the graduated scale. The differencebetween the two readings in the height of the second container willgive, in millimeters of mercury, the pressure or partial vacuum whichhas been measured.

By housing the first container in an enclosed area which can be exposedboth to the atmosphere and to one of two different pressures, it ispossible by means of the aforesaid essential construction to measure thedifference between these two pressures. In this use of the apparatus,after it has been initially prepared as aforesaid, the lower of the twopressures is applied to the enclosed area, while the other pressure isapplied to the mercury level in the second container. When theequilibrium of the balance is restored and the reading of the graduatedscale taken, the difference in the two heights of the second containerwill give in millimeters of mercury the differential pressure measured.

It has been found that the manometer embodying the invention isextremely accurate, to about 0.5 thousandths, since readings of liquidlevels which are difficult to perform with accuracy, are replaced bymeasurements of height on a graduated scale, and by measurements of abalance which can be made extremely accurate by the use of a highprecision balance provided with a measuring vernier.

It is believed that characteristics and advantages of the manometer ofthis invention will be better understood from a consideration of thefollowing description when read in connection with the accompanyingdrawings, in which FIG. 1 is is an elevational schematic view of oneform in which the apparatus may be constructed to measure a pressurediffering from the atmosphere; and

FIG. 2 is a similar view showing how the apparatus may be utilized tomeasure differential pressure.

In both figures of the drawings, similar reference numerals have beenapplied to parts which are the same, or substantially the same in bothconstructions. Referring now more particularly to FIG. 1 of thedrawings, the container which has heretofore been referred to as the"first container" is generally designated 1, and the other containerwhich has heretofore been referred to as the second container" isgenerally designated 5. The container 1 is seated on the tray 12 of abalance 2 of any suitable construction. Inserted into the open mouth ofthe container 1 and extending down into such container to a point shortof the bottom of the latter, is a vertical end portion 3 of a rigid pipe3 having-a U-shaped upper end. The other leg 3" of the pipe 3 extendsdownwardly substantially below the container 1 to and is connected tothe lower end of a flexible pipe 4 which has a practically constantvolume no matter what its position or condition. In the form shown inFIG. 1 the flexible pipe 4 is spring shaped so that its upper end may bemoved relative to its lower end without change in its volume. The upperend of the flexible pipe 4 is connected to the bottom end of thecontainer 5. It will be noted that the container 5 is constructed tohave reduced lower and upper end portions 13 and 14, respectively, andan enlarged central portion in which is located the mercury level. Thecontainer 5 is supported by two arms 15 which are connected at theirinner ends to the reduced end portions 13 and 14 of such container andwhich are both threadedly connected intermediate their ends to athreaded vertical rod 6 provided at its upper end with a manuallyoperable handle 7. The outer ends of the two arms 15 are slidablyconnected to a vertical guide bar 16. The enlarged central portion ofcontainer 5 carries a vernier 17 arranged to slide along the divisionsor graduations on the main vernier scale 8. It will thus be seen that bymanipulating the handle 7, the height of the second container 5 may bevaried, and such height may be read accurately on the vernier scale 8.The graduations on the scale 8 are in millimeters of mercury and extendsufficiently both above and below the first container 1 to take care ofthe range of movements of the second container 5 in measuring the rangeof pressures for which the apparatus was designed.

The upper end of the container portion 14 is connected through aspirally-shaped flexible pipe 9 to a nozzle 10 provided on the lower endof a chamber 18 connected through a valve 19 to the atmosphere andthrough a valve 20 to the source of pressure which is to be measured.When the valve 20 is closed and valve 19 opened, the container 5 throughthe chamber 18, nozzle 10 and pipe 9, is exposed to atmosphericpressure. In this condition of such parts, the container 5 is raised tothe level of container 1 in order to receive the supply of mercury 21which is to be contained in container 1, pipe 3, pipe 4 and container 5.The mercury is added until the levels thereof in the two containers 1and 5 reach the mid-heights thereof which are identical. The balance 2is then placed in equilibrium by means of the weights 11 in whichcondition thereof the printer 22 of the balance will be at 0 position.The height of the container 5 is then taken on the graduated scale 8.

After the apparatus has been prepared in the manner above described, thevalve 19 is closed and the valve 20 opened to expose the mercury incontainer 5 to the low pressure or partial vacuum which it is desired tomeasure. When the mercury in container 5 is so exposed to the pressureto be measured, there is caused a variation in the levels of mercury inboth containers 5 and 1. As the volume of mercury in container 1changes, the balance 2 will become unbalanced. ln orderto restore theequilibrium of the balance, the container 5 is moved vertically in adirection to attain this result. As this is done, the original quantityof mercury 21 in container 1 will be restored. Consequently, the levelsof mercury in both containers 1 and 5 will return to their exactoriginal positions therein. When the equilibrium of the balance isrestored by so changing the height of container 5, the new height ofsuch container is read on the graduated scale 8. The difference betweenthis reading and the original reading for the container will give inmillimeters of mercury, an exceedingly accurate measurement of thepressure to which the container 5 is connected through valve 20.

In the aforesaid practice of the invention, it should be noted that thevolumes of the containers above and below the levels of mercuryestablished therein during the supply of such mercury at atmosphericpressure, must be suflicient to take care of the variations in volume ofthe mercury displaced between the two containers at the maximum andminimum of the range of pressure which the apparatus is designed tomeasure. Further, the cross-sectional area of container 1 should besufficiently large so that errors in the weight of mercury which occurdue to the inaccuracy of the balance 2, will result only in variationsin the mercury level in this container that are within the degree ofmeasured accuracy required. The crosssectionalare'a of the enlargedportion of container in which the mercury level is located should besufficiently large so that any variation in the volume of the flexiblepipe 4 because of its deformation due to the displacement of thecontainer 5, will only produce a negligible variation of the mercurylevel in such container. Also such cross-sectional area of the enlargedportion of container 5 should be sufficient to effect the transfer intocontainer 1 of a measurable quantity of mercury with the required degreeof accuracy, when the height of container 5 is varied.

Considering now the embodiment shown in FIG. 2 of the drawings, it willbe noted that the balance 2, container 1, and the U-shaped upper end ofrigid pipe 3 are contained within an enclosed area or chamber 25 whichmay be connected by means of a pipe 26 and valve-27 to the source of thelower of two pressures whose difference is to be measured. The leg 3" ofthe rigid pipe 3 leaves the enclosed area 5 through a seal 28. Thechamber 25 should be sized and constructed to resist those pressures towhich it is subjected.

Instead of the container 5 carrying a vemier 17 and being controlled inits movements by a guide bar 16 and guide members provided on the outerends of its supporting arms 15,15 as in the embodiment of FIG. 1, inthe'embodiment of FIG. 2

, the vernier scale 8 performs a dual function. That is, the

vemier 17 is mounted on the outer ends of the arms 15,15 and isconstructed in the form of a slide so that the scale 8 7 functions bothas the main graduated scale and a guide post.

The vemier scale 8 and the threaded rod 6 and handle 7, however, performthe same functions as the vemier scale 8, threaded rod 6, handle 7 andpost 16 in the embodiment of FIG. 1. The lower part of container 5 isconnected by means of a flexible pipe 4 in the fonn of a suppletube tothe lower end of the leg 3" of the rigid tube 3. The upper part ofcontainer 5 is connected by means of a flexible pipe 9' to a pipesection 29 which is co'nnectedby a pipe 30 and valve or tap 31 to thechamber 25. The pipe section 29 is also connected by a valve or tap 32to a nozzle 10 provided on a chamber 18 which is connected by a valveortap 19 to the atmosphere and by a valve or tap 20 to the source of thehigher of the two pressures whose difference is to be measured.

In preparing the apparatus of FIG. 2 for operation, tap 27 is closed,taps 31 and 32 are opened, and tap 20 is closed and tap 1.9 opened sothat both the chamber and the two containers 1 and 5 are exposed toatmospheric pressure. Then in the manner described with respect to theembodiment of FIG. 1, the container 5 is placed at the same level ascontainer 1, the whole unit constituted of the container 5, pipe 4, pipe3 and container 1 is filled with mercury 21 up to approximatelymidheight of the two containers so that the two mercury levels areidentical, the balance is placed in a position of equilibrium by weights1] so that the scale index 22 is at position 0, and then the height ofcontainer 5 is read from the graduated scale 8'.

r In measuring the differential pressure, tap 32 is closed while leavingtap 31 open so that the enclosed area 25 remains in contact withcontainer 5 through the flexible pipe 9'. Tap 27 is then opened toexpose the enclosed area 25 to the lower of the two pressures whosedifference is to be measured, this pressure acting equally on themercury levels in the containers 1 a and 5. A check is made to ensurethat the balance 2 remains in equilibrium and that there is no leak orfault in the apparatus which might lead to incorrect measurements. Thetap 31 is then closed to isolate the container 5 from the enclosed area25. Tap 19 is closed and tap 20 opened to bring the chamber 18 intocommunication with the higher of the two pressures being measured. Tap17 is then opened to permit the higher pressure to exert its force onthe mercury level in container 5. This increased pressure on suchmercury level has the efiect of displacing a certain quantity of mercuryinto container 1 and, consequently, of disturbing the equilibrium of thebalance 2. Container 5 is then displaced to restore the balance 2 to itsposition of equilibrium and so that the level of mercury in container 1regains its original position; The new height of the container 5 is thenread from the graduatedscale 8'. The difference between the two heightsof the container 5 will give, in millimeters of mercury, thedifferential pressure measured.

I claim: 1

1. A high precision mercury manometer comprising a first containerholding mercury at a given level under atmospheric pressure, means forbalancing said container with the mercury therein at said given level, asecond container holding mercury, means supporting said second containerfor vertical movement, tubular means connecting said first container tosaid second container comprising an end portion of a rigid pipe insertedvertically down into the mercury in said first container, and a flexibleportion between said rigid pipe and said second container, said tubularmeans being connected to the bottom of said second container, beingfilled with mercury and having a practically constant volume regardlessof the deformation. thereof caused by changes in position of said secondcontainer, means for exposing the mercury in said second container toatmospheric pressure, or to a second pressure, the level of the mercuryin said second container under atmospheric pressure being at the sameheight as the mercury level in the first container when the twocontainers are at the same height, and changing to a different heightwhen exposed to said second pressure to change the quantity of mercuryin said first container and to unbalance said balancing means, saidsupporting means being operable to move said second container to anotherposition at which said balancing means is restored to balance while themercury in such container is being subjected to such second pressure,and means for measuring the different heights of the second container.

2. A mercury manometer as defined in claim 1, in which said secondcontainer has an enlarged central portion in which the mercury level islocated, and reduced upper and lower end portions, and in which saidtubular means is connected to said reduced lower end portion, and inwhich said pressure exposing means is connected to the reduced upper endportion of said second container and comprises fixed pressure supplyingmeans and flexible tubular means between said fixed means and saidreduced upper end portion.

3. A mercury manometer as defined in claim 2, in which said supportingmeans comprises a micrometer adjusting device having a verticallymovable element, and means for supporting said second container on saidmovable element.

4. A mercury manometer as defined in claim 2, in which said measuringmeans comprises a vertically disposed main scale having graduations inmillimeters of mercury extending both above and below the level of saidfirst container, and a vemier coacting with said main scale andconnected to said second container for movement therewith.

5. A mercury manometer as defined in claim 1, including a sealed chambercontaining said first container, said balancing means, and a portion atleast of said rigid pipe, second means for exposing said chamber eitherto atmospheric pressure, or to a third pressure whose difference withsaid second pressure is to be measured, and means for bringing apressure in said sealed chamber into communication with said secondcontainer to expose the mercury level therein to such pressure.

6. A mercury manometer as defined in claim 5, in which said firstmentioned pressure exposing means comprises fixed pressure supplyingmeans and flexible tubular means between said fixed means and saidsecond container, and in which said means for bringing a pressure in thesealed chamber into communication with said second container comprisessecond tubular means connecting said sealed chamber with said firstpressure supplying means, and means for controlling the application ofpressure from either said sealed chamber, or said first mentionedpressure exposing means to the mercury level in said second container.

7. The method of measuring a pressure or partial vacuum which comprisestaking a unit composed of two mercury reservoirs connected by partiallyflexible tubing one end of which extends down into one of suchreservoirs and the other end of which is connected to the bottom of theother reservoir, placing the two reservoirs at the same height whileexposing them to atmospheric pressure, then filling the unit withmercury until both reservoirs are approximately half full and themercury is at identical levels in both reservoirs, then balancing theone reservoir and taking the height of the other reservoir inmillimeters of mercury, then exposing the mercury level in the otherreservoir to a second pressure to be measured thereby causing adisplacement of mercury between the two reservoirs and an unbalancing ofthe balance, displacing the other reservoir in a direction to restorethe balance to balanced condition, then taking the new height of theother reservoir in millimeters of mercury, and finally taking thedifference between the two heights of the other reservoir in millimetersof mercury.

8. The method defined in claim 7, including the steps of exposing themercury in both reservoirs to a third pressure after it has been exposedto atmospheric pressure and while the mercury levels in both reservoirsare at identical heights and the one reservoir is balanced, and thenwhile maintaining the mercury level in said one reservoir exposed to thethird pressure, exposing the mercury level in the other reservoir tosaid second pressure to cause said displacement of mercury between thetwo reservoirs.

1. A high precision mercury manometer comprising a first containerholding mercury at a given level under atmospheric pressure, means forbalancing said container with the mercury therein at said given level, asecond container holding mercury, means supporting said second containerfor vertical movement, tubular means connecting said first container tosaid second container comprising an end portion of a rigid pipe insertedvertically down into the mercury in said first container, and a flexibleportion between said rigid pipe and said second container, said tubuLarmeans being connected to the bottom of said second container, beingfilled with mercury and having a practically constant volume regardlessof the deformation thereof caused by changes in position of said secondcontainer, means for exposing the mercury in said second container toatmospheric pressure, or to a second pressure, the level of the mercuryin said second container under atmospheric pressure being at the sameheight as the mercury level in the first container when the twocontainers are at the same height, and changing to a different heightwhen exposed to said second pressure to change the quantity of mercuryin said first container and to unbalance said balancing means, saidsupporting means being operable to move said second container to anotherposition at which said balancing means is restored to balance while themercury in such container is being subjected to such second pressure,and means for measuring the different heights of the second container.2. A mercury manometer as defined in claim 1, in which said secondcontainer has an enlarged central portion in which the mercury level islocated, and reduced upper and lower end portions, and in which saidtubular means is connected to said reduced lower end portion, and inwhich said pressure exposing means is connected to the reduced upper endportion of said second container and comprises fixed pressure supplyingmeans and flexible tubular means between said fixed means and saidreduced upper end portion.
 3. A mercury manometer as defined in claim 2,in which said supporting means comprises a micrometer adjusting devicehaving a vertically movable element, and means for supporting saidsecond container on said movable element.
 4. A mercury manometer asdefined in claim 2, in which said measuring means comprises a verticallydisposed main scale having graduations in millimeters of mercuryextending both above and below the level of said first container, and avernier coacting with said main scale and connected to said secondcontainer for movement therewith.
 5. A mercury manometer as defined inclaim 1, including a sealed chamber containing said first container,said balancing means, and a portion at least of said rigid pipe, secondmeans for exposing said chamber either to atmospheric pressure, or to athird pressure whose difference with said second pressure is to bemeasured, and means for bringing a pressure in said sealed chamber intocommunication with said second container to expose the mercury leveltherein to such pressure.
 6. A mercury manometer as defined in claim 5,in which said first mentioned pressure exposing means comprises fixedpressure supplying means and flexible tubular means between said fixedmeans and said second container, and in which said means for bringing apressure in the sealed chamber into communication with said secondcontainer comprises second tubular means connecting said sealed chamberwith said first pressure supplying means, and means for controlling theapplication of pressure from either said sealed chamber, or said firstmentioned pressure exposing means to the mercury level in said secondcontainer.
 7. The method of measuring a pressure or partial vacuum whichcomprises taking a unit composed of two mercury reservoirs connected bypartially flexible tubing one end of which extends down into one of suchreservoirs and the other end of which is connected to the bottom of theother reservoir, placing the two reservoirs at the same height whileexposing them to atmospheric pressure, then filling the unit withmercury until both reservoirs are approximately half full and themercury is at identical levels in both reservoirs, then balancing theone reservoir and taking the height of the other reservoir inmillimeters of mercury, then exposing the mercury level in the otherreservoir to a second pressure to be measured thereby causing adisplacement of mercury between the two reservoirs and an unbalancing ofthe balance, displacing the other reservoir in a direction to restorethe balance to balanced condition, then taking the new height of theother reservoir in millimeters of mercury, and finally taking thedifference between the two heights of the other reservoir in millimetersof mercury.
 8. The method defined in claim 7, including the steps ofexposing the mercury in both reservoirs to a third pressure after it hasbeen exposed to atmospheric pressure and while the mercury levels inboth reservoirs are at identical heights and the one reservoir isbalanced, and then while maintaining the mercury level in said onereservoir exposed to the third pressure, exposing the mercury level inthe other reservoir to said second pressure to cause said displacementof mercury between the two reservoirs.